// Feature 1 — a pack element exposes ONLY the constraint protocol's interface.
// `xs[i].v` reaches a concrete field of IntCell that is not part of `Box`, so
// it's rejected even though IntCell does have `v` — a pack element is viewed
// through the protocol, like a constrained generic. (Protocol methods like
// `get()` ARE callable; see examples 193/194.)

#import "modules/std.sx";

Box :: protocol(T: Type) {
    get :: () -> T;
}
IntCell :: struct { v: i64; }
impl Box(i64) for IntCell { get :: (self: *IntCell) -> i64 => self.v; }

leak :: (..xs: Box) -> i64 {
    return xs[0].v;   // `v` is not part of Box — error
}

main :: () -> i32 {
    print("{}\n", leak(IntCell.{ v = 5 }));
    0
}